Supplying a certain discharged pressurized liquid of one hydraulic pump to many actuators may be achieved in the following way: providing a plurality of hydraulic reversing valves in a discharge path of the hydraulic pump, and supplying the pressurized liquid to the actuators by switching the hydraulic reversing valves. When the pressurized liquid is to be simultaneously supplied to many actuators, the liquid will be preferentially supplied to actuators having a low load pressure and, correspondingly, liquid supplied to actuators having a relatively high load pressure will be reduced or cut off.
To solve this problem, most of the hydraulic circuits are provided with pressure compensation valves between the hydraulic reversing valves and the actuators, and a maximum load pressure among all of the actuators is detected and applied to the pressure compensation valves so that the exit pressure of each of the hydraulic reversing valves is uniformly increased to be substantially the same as the maximum load pressure. Thereby, when the hydraulic reversing valves are operating simultaneously, the pressurized liquid passing through the hydraulic reversing valves is supplied to the actuators at an allocation rate proportional to the open area of each of the hydraulic reversing valves.
A pressure compensation valve disclosed in Chinese Patent CN1159849A comprises: a valve for establishing or blocking a connection between an inlet and an outlet; a pressure chamber; a piston, being driven by a load pressure from the chamber and pushing the valve in the blocking direction; an intermediate pressure chamber, being connected to the inlet via a first conduit and pushing the valve in the blocking direction by the pressure therein; and a pressure-variable reducing valve, being adapted to release a pressurized fluid in the intermediate pressure chamber via the second conduit. However, compensation features required by some actuators will vary; some compensation valves can also function as check valves, or some compensation valves cannot change the pressure compensation features, or although some compensation valves can both function as the check valves and change the compensation features, the structure thereof is too complicated and the cost thereof is relatively high.